Environmentally clean process for utilizing pyrolysis products

ABSTRACT

A process for the recovery of sulfur from the products resulting from the pyrolysis of sulfur-containing organic materials, comprises the steps of: a) carrying out the combustion of liquid pyrolysis products, thereby to obtain sulfur dioxide in the formed exhaust gases; b) reacting hydrogen sulfide recovered from gases, generated in the pyrolysis process, with said sulfur dioxide; and c) reacting hydrogen sulfide recovered from gases, generated in the gasification of solid pyrolysis products, with said sulfur dioxide, and as a result to obtain elemental sulfur, pure gaseous fuel and exhaust gases from liquid products combustion free from sulfur-containing compounds.

FIELD OF THE INVENTION

The present invention relates to an energy-efficient and environmentallyfriendly process for the pyrolysis of sulfur-containing organicmaterials. More particularly the invention relates to processes for therecycling of sulfur-containing products, such as vulcanized polymers. Aparticularly interesting process of this type is the recycling of usedtires by a process that does not release sulfur containing compoundsinto the atmosphere.

BACKGROUND OF THE INVENTION

Many methods for the conversion of discarded tires are known in the art,to produce useful products such as fuels. Also known in the art aremethods for cleaning obtained products from polluting compounds.However, process known in the art suffer from a variety of drawbacks,such as they release polluting gaseous sulfur compounds into theatmosphere or require expensive purification steps to remove them priorto the release of exhaust gases. Other processes end with other liquidor gaseous polluting discharges or require cleaning steps that are noteconomically efficient; furthermore, prior art processes often fail toexploit the pyrolysis products in an efficient manner.

For instance, U.S. Pat. No. 4,240,587 discloses a process, in which thetires are first cryogenically fragmented and then pyrolysed at 450-500°C. in a rotary inclined cylinder, which is heated indirectly. Theremaining pyrolysis oil may either be further utilized as an initialcomponent for manufacturing chemical compounds, such as lubricants, orit may be used as a fuel propellant. The remaining pyrolysis gas isutilized for the direct operation of a gas turbine. However, all thesuggested products of this invention contain sulfur and therefore theircombustion products cause sulfur dioxide pollution of the atmosphere.

An illustrative cleaning process is found in UShttp://patft.uspto.gov/negacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&1=50&s1=4,806,232.PN.&OS=PN/4,806,232&RS=PN/4,806,232-h0#h0http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&1=50&s1=4,806,232.PN.&OS=PN/4,806,232&RS=PN/4,806,232-h2#h24,806,232,which describes a method for the desulphurization of sulfur-containingheavy fuels or used oil, in which the fuels are mixed with solid basicadditive (preferably lime) and metal in finely divided form (preferablyiron powder). The mixture obtained is injected into the pyrolysis andthe sulfur is absorbed or chemically bonded to the basic additive andseparated. The permanent gas formed in the pyrolysis and thesimultaneously formed condensate may be directly fired as low-sulfurfuel. This method is expensive and cumbersome to perform and, therefore,has not found broad application in the art.

It is therefore clear that it would be highly desirable to provide asimple process by which pyrolysis products can be obtained, which arefree from harmful sulfur product or could be used as fuels withoutrelease into the environment of harmful sulfur-containing products.

It is therefore an object of the present invention to provide a processthat overcomes the drawbacks of the prior art. It is another object ofthe invention to provide an environmentally-friendly process for therecycling of sulfur-containing high-molecular and other organicmaterials. It is yet another object of the invention to provide anefficient recycling process that maximizes the utilization of theproducts of pyrolysis.

Other objects and advantages of the invention will become apparent asthe description proceeds.

SUMMARY OF THE INVENTION

In an aspect of the present invention there is provided a process forthe recovery of sulfur from the products resulting from the pyrolysis ofsulfur-containing high-molecular weight organic material, comprising thesteps of:

-   -   a) carrying out the combustion of liquid pyrolysis products,        thereby to obtain sulfur dioxide;    -   b) reacting hydrogen sulfide recovered from gases generated in        the pyrolysis process with said sulfur dioxide; and    -   c) reacting hydrogen sulfide recovered from generator gases, if        any, with said sulfur dioxide;        thereby to obtain elemental sulfur, gaseous products essentially        free from hydrogen sulfide and exhaust gases essentially free        from sulfur dioxide.

According to one embodiment of the invention sulfur dioxide is containedin diesel exhaust gases formed in a diesel electro-generator.

The invention can be usefully exploited in a process for the treatmentand utilization the products of the pyrolysis of sulfur-containing highmolecular weight organic materials, to generate electric power withoutenvironmental contamination and without the formation of non-usableby-products. The process includes the gasification of the solid organicmaterials and the use of the produced hot gas, together with pyrolysisgas, as a direct heat carrier for a pyrolytic reactor, and thesubsequent use of both gas mixtures, after cleaning from hydrogensulfide, for electric power generation.

In another embodiment of the invention the processing of hydrogensulfide produced resulting from processes pyrolysis and gasificationaccordingly the known Claus process is not needed for the thermal stageof the process for obtaining sulfur dioxide, as it is done usually inthe Claus process (and as described e.g. in: Ulmann's Encyclopedia ofIndustrial Chemistry, 2003, Sixth, Completely Revised Edition, volume34, pp. 605-627). Thus, such very complicated thermal stage iseliminated.

In the process of the present invention only the second, catalyticstage, of the Claus process:

2H₂S+SO₂→3S+2H₂O

is in principle used. This reaction runs over a catalyst: activatedalumina at 240-330° C. in different steps of the process. The stream ofhydrogen sulfide interacts with exhaust gases from the liquid productcombustion, which contain sulfur dioxide. For the complete purificationof the exhaust gases from H₂S residue, the third sub-stage is used foroxidizing H₂S directly over a suitable catalyst according to thereaction:

2H₂S+O₂=2S+2H₂O.

In the final stage the exhaust gases undergo treatment by a suitablesorbent.

In an embodiment of the present invention the total physical heat of theexhaust gases, those containing sulfur dioxide, and those that do notcontain sulfur dioxide (formed in a clean gaseous fuel combustion) isenough for the said total catalytic process, i.e., an additional heatsource is not required for heating the reaction mixtures after theircooling at each stage of the process for sulfur vapors condensation.This obviates also the need for equipment for heating the reactionmixture, which is a prerequisite in the classical Claus method.

In another aspect the invention encompasses an efficient electricalpower production process, wherein:

-   -   (a) the fuels are gaseous and liquid products of the organic        material (e.g., discarded tire shreds) pyrolysis, and the        gaseous product of the pyrolysis solid product gasification;    -   (b) the liquid product obtained from a pyrolysis step is used        directly for power production;    -   (c) the solid carbonized product is gasified in a gas generator        resulting in gaseous fuel (generator gas) containing hydrogen        sulfide. The hot generator gas, which is partially cooled by        mixing with cool gas of the total process, is directed into the        pyrolysis reactor as a heat carrier;    -   d) the mixture of gases, formed through the pyrolysis of raw        material, and said gaseous heat carrier outgoing from the        pyrolysis reactor together with the formed vapors, after cooling        and separation from condensed liquid product, undergoes        purification from hydrogen sulfide by known methods, e.g., by        the monoethanolamine process. After this step two streams are        obtained: the separated hydrogen sulfide stream and the mixed        cleaned gas that is used as a fuel for electric power        generation;

(e) the exhaust gases resulting from the combustion of the liquidpyrolysis products, which contain sulfur dioxide, are interacted withthe said separated hydrogen sulfide stream, resulting in sulfur-freefinal exhaust gases, and sulfur as a recycled product.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a total pyrolysis processaccording to one embodiment of the present invention; and

FIG. 2 is a detailed illustration of the sulfur recycling processaccording to one embodiment of the process of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The process that is schematically illustrated in FIGS. 1 and 2 can becarried out using a variety of different equipment and arrangements and,as will be apparent to the skilled person, is not limited to anyparticular arrangement of equipment and process steps, as long as thecomposition resulting from the process at its outlets is essentiallycomparable to the one that will be described in greater detailhereinafter.

Without departing from the generality of the above, one exemplaryprocess will be described in greater detail, with reference to FIG. 1,which is a schematic flow sheet of a pyrolytic process for discardedtires, provided for the purpose of illustration.

The discarded tires are pyrolysed in a pyrolytic reactor after havingbeen shredded into large pieces of size 250-300 mm, which are fedthrough a feeding system schematically indicated at numeral 1. Thepyrolysis reactor can be of any suitable type and is therefore notdescribed herein, for the sake of brevity. In the reactor the tirepieces are heated up to a typical temperature of 480-500° C., e.g., by agaseous heat-carrier indicated at 2. The heat-carrier is preferably—butnot limitatively—a gas 10 produced by the gasification of the solidcarbonized product 7 and partly cooled by mixing in a mixing chamber,using cooled and cleaned final gases, up to 650-700° C.

In the example of FIG. 1 the hot heat-carrier passing through thepyrolysis reactor is partially cooled by its contact with the tirepieces and is mixed in the reactor with the gases and vapors formedduring tire shreds pyrolysis. The combined stream leaves the reactor atnumeral 3 and is cleaned from dust in a dedicated separator 4, forexample a Vortex system, manufactured by Vortex Co., Israel. Then thevapor-gas stream 4 is directed to a system for cooling and vaporcondensation, which includes two stages. In the first stage thevapor-gas stream is cooled in an air cooler by means of air stream 8,directed from a source of air, typically up to about 130° C. Here partof the vapors is condensed. The cooler provides also flushing of thevapor-gaseous stream from the remainder of dust, by part of condensateformed in the process. The hot air 13 leaving the cooler is directed tothe gas generator, where its heat is utilized, thus utilizing part ofthe heat of the vapor-gaseous pyrolysis products and of the gasifyinggases. The formed liquid and the stream of gas and of non-condensedvapors 14 from the air cooler enter the gas-liquid separator, afterwhich the first liquid product 15 is directed for treatment to acentrifuge, where the liquid is cleaned from the last dust, and isdirected to its oil collector. The gas and non-condensed vapors 16 enterthe second stage cooler-condenser, where it is cooled to about 15-20° C.The condensed second liquid and the gas come into a separator (see 17)and after their separation are directed as follows: the gas 22—tocleaning from hydrogen sulfide and the liquid product is directed to itscollector or is mixed with heavier liquid 19. The produced oil is readyto be used as a fuel for diesel or other electro-generators, accordinglythe requirements for their type of engine. This fuel combustion, aspreviously mentioned, is accompanied in the prior art by the emission ofsulfur dioxide in the exhaust gases. The sulfur recovery processaccording to the invention solves the environmental problems associatedwith the use of said liquid fuels, as further discussed below.

The cooled gas separated from the oil, as hereinbefore mentioned, entersat numeral 22 into a system where it is cleaned from hydrogen sulfide bymonoethanolamine. The clean gas can be combusted without damage to theenvironment and is used as a gaseous fuel for electric power generationby means of electro-generators. Illustrative examples of such generatorsare, for example, those manufactured by GE Jenbacher GMBH & CO OHG(Austria) with gas engines from 342 kWe up to 3,119 kWe. Part of thecleaned gas is directed to a mixing chamber for partially cooling thehot gas stream 10 from the gas generator and preparing the heat carrier11 for the pyrolysis reactor. Another part of the cooled and cleaned gas25 acts as a fuel in a burner for a heat exchanger, which is used tocontrol the final temperature of the gaseous heat carrier 2 that is fedto the pyrolytic reactor.

The recovered hydrogen sulfide 24 is reacted with exhaust gases 21obtained from the combustion of the liquid fuel obtained from thepyrolysis. The reaction runs as a modified Claus catalytic reaction, asalready discussed above. The resulting exhaust gases are sulfurdioxide-free and are non-polluting.

The sulfur that is formed in the reaction between hydrogen sulfide andsulfur dioxide (from the exhaust gases), is collected and is amarketable product.

The solid pyrolysis product formed during the pyrolysis of discardedtire shreds, is evacuated at 6 from the reactor; it comprises solidcarbonized material and steel cord in the form of wire. The carbonizedmaterial is fragile and when treated in a suitable crusher, such as ahammer crusher, it can be readily reduced in size and thereafterseparated from the cord by sieving or by electromagnetic separation. Thecrushed carbonized solid product separated from cord steel is directedat 7 to rising- or fluidized bed gasification and the cord steel can berecycled.

The solid carbonized product gasification can be carried out as asteam-air (respectively 9-13) process without the introduction ofexternal heat. Resulting from such process, taking place at temperaturesaround 1,000° C., a semi-water generator gas is formed. The generatorgas 10 undergoes cleaning from dust in a cyclone system known per se inthe art and therefore not described herein in detail. Further, thegenerator gas is partial cooled by its mixing with cool gas 25 so thatthe temperature of the mixture is decreased to 650-700° C. The mixtureof gases so obtained is a gaseous heat carrier 2, which can be used toheat the pieces feedstock in the pyrolytic reactor.

The above description, as stated, is not intended to limit the inventionin any way but it does provide a more comprehensive understanding of apractical scenario in which the invention can be advantageouslyimplemented. Of course, the skilled person will be able to devisealternative scenarios and setups in which the invention can beadvantageously carried out.

Reverting now to FIG. 2, the process of the present invention for thesulfur regeneration is shown in detail. The regeneration of sulfurcomprises:

-   -   a) The recovery of hydrogen sulfide contained in gaseous        products resulting from the pyrolysis of sulfur-containing        organic material, as well as in gases resulting from        gasification of solid pyrolysis product;    -   b) The recovery of sulfur contained in sulfur-organic compounds        present in liquid products.

According to the present invention hydrogen sulfide 24 (FIG. 1)recovered from pyrolysis and generator gases interacts with sulfurdioxide, which is contained in exhaust gas 21 (FIG. 1) formed in anelectro-generator during the combustion of liquid pyrolysis products.The reaction is a modified Claus catalytic reaction that runs throughthree sub-stages. The molar ratio H₂S to SO₂ in the reaction mixtureentering the first sub-stage is up to 3.7. The operating temperature inthis sub-stage is preferably about 320° C. This temperature promotes thehydrolysis of COS and CS₂, which can be formed during the liquid fuelcombustion. Activated alumina, which is the known Claus catalyst, isused. With this catalyst the H₂S oxidation by oxygen present in theexhaust gases (in a small amount) is minimal. The gaseous reactionmixture after cooling, and the formed sulfur condensation, are fed tothe second sub-stage which is previously heated in heater 210; thereaction runs at 200-220° C. over a mixture of alumina and titaniumdioxide catalysts where the reaction between residual hydrogen sulfideand sulfur dioxide reaches completion. The processing exhaust gas stillcontains residues of H₂S. In order to remove said H₂S the residualhydrogen sulfide is directly oxidized into sulfur over the appropriatecatalyst. This can be done by means known in the art; for instance, U.S.Pat. No. 5,262,135 discloses a complete stage of the Claus process ascontacting the tail gas preliminary admixed with oxygen and heatedpreferably up to 220° C. in a fixed bed with a catalyst comprising atleast 80% by weight TiO₂ and containing of an impregnate selected fromthe group consisting of nickel, iron and cobalt. In this case air isintroduced into the processed stream and hydrogen sulfide is oxidizedaccordingly the reaction

2H₂S+O₂→2S+2H₂O

After the said reaction the stream is cooled to obtain sulfurcondensation. In one embodiment of the invention it is preferred toorganize the oxidizing stage using the known Superclaus catalyst—ironand chromium oxides supported by α-alumina or silica (described inUlmann's Encyclopedia of Industrial Chemistry referred to above) orusing the catalyst disclosed in U.S. Pat. No. 6,506,356, that do notdepend on the presence of steam.

In principle, according to WO 1987/002653, a practically completeafter-treatment is achieved in the last stage by passing the gasesthrough the solid metal oxide sorbent, e.g. zinc oxide, combined with aporous carrier material and iron, cobalt and nickel oxides with furtherregeneration of the sorbent. According to the present invention thetemperature (usually about 450° C.) and heat content of both exhaustgases (21 and 26, FIG. 1) is sufficient for carrying out all stages ofthe modified Claus catalytic reaction. This obviates the need foradditional heat and heating equipment for in each sub-stage of theprocess, which is a prerequisite in the classical Claus method.

Process Description

The process flow diagram for sulfur recovery according to one embodimentof the invention is shown in FIG. 2. The exhaust gases 202 and 202.1(21, 26 in FIG. 1) from the electro-generators enter the heater 210(FIG. 2) of the second sub-stage of the process. Here they heat thereaction mixture 209, formed after cooling the stream in the firstsub-stage by cooler 207, from 140° C. up to 200-220° C. Then thepartially cooled exhaust gas 202 (21 in FIG. 1) containing sulfurdioxide is fed to the mixing and heating into a chamber 203, where itmixes with the hydrogen sulfide stream and thus a hot reaction mixtureis formed for the first sub-stage of the catalytic reaction of hydrogensulfide with sulfur dioxide contained in the exhaust gas; if it isnecessary to raise the temperature of the reaction mixture, the cleanexhaust gas 202.1, which is free of sulfur dioxide, goes through a heatexchanger of the chamber 203 and heats the said reaction mixture.

The reaction mixture 204 enters reactor 205, where the Claus catalyticreaction takes place over an activated alumina catalyst. According toone alternative embodiment of the invention instead of a fixed bedreactor-converter a rotating horizontal reactor-converter is used. Therotating reactor is equipped with a horizontal shaft provided withmixing blades. At low speed of rotation (0.2-3 rpm) sufficient mixing isachieved while avoiding catalyst abrasion and improving the contactbetween gaseous reaction mixture and the catalyst surface. Applicationof modern catalysts in the form of balls with a diameter 4.8 mm and morehaving enough high strength showed a slight dust formation in an actualtest. The feeding of the gaseous reaction mixture is carried out througha distribution manifold installed outside the reactor at its bottom. Thegases leave through the outlet pipe in the upper part of the reactor andfurther pass through the said Vortex chamber for cleaning from the saidslight amount of dust. A periodic withdrawal of part of the spentcatalyst for regeneration is performed simultaneously with itscompletion without stopping the reactor by means of charging anddischarging lock chambers preventing leaking the gases into theatmosphere.

After leaving the reactor, stream 206 containing the formed sulfur iscooled down to 140° C. in cooler 207, the condensed sulfur is separatedfrom the gas stream in liquid state and is removed at 208 from thecooler. The reaction mixture is fed (at 209) to the second sub-stage ofthe catalytic reaction. Here the mixture is heated again in the heater210 by exhaust gas streams 202 and 202.1, as previously discussed, andenters the reactor 212 (at 211) for the second sub-stage of thecatalytic reaction over alumina and titanium dioxide catalysts. Then themixture 213 leaves the reactor 212 and is cooled in cooler 214 down tothe temperature required for sulfur condensation (140° C.), separatedand removed (215). Furthermore air is injected into the reaction mixtureand the mixture is heated again up to 220° C. in a heater 217 by meansof the exhaust gas 202.1 leaving the first sub-stage heat exchanger(placed in chamber 203). The heated reaction mixture is fed to reactor219 for the direct oxidation of the tail hydrogen sulfide with sulfurformation, over the Superclaus catalyst or over the catalyst containingoxides of vanadium, titanium, and of element selected from group of Fe,Mn,Cr, Ni, Sb and Bi (see U.S. Pat. No. 6,506,356).

For reliability in the complete purification the processed exhaust gases202 from hydrogen sulfide they are passed through a sorbent consistingof activated carbon, particularly the granular non-impregnated GCSulfursorb Plus for H₂S Treatment or the Spectrum XB-17 (50/50 blend ofactivated carbon with granular media impregnated with potassiumpermanganate) which are produced in General Carbon Corp., USA. AQIVID(Air Quality Management District) publishes results of Carbon ScrubberHydrogen Sulfide Removal Performance (2006 year), wherein when the inletELS concentration in air is 10-20 ppm the outlet concentration can bebetween 0.01-0.1 ppm (the allowable concentration is 1 ppm). Thisdemonstrates the possibility of complete after-purification of exhaustgases from H₂S.

EXAMPLE

Checking the Interaction of Exhaust Gases, Resulting from the Combustionof Pyrolysis Liquid Fuel in a Diesel Engine and Containing SulfurDioxide, with the Stream of Hydrogen Sulfide.

The liquid fuel was produced from the pyrolysis of discarded tire shredsin an experimental, 7 liter reactor. The final pyrolysis temperatureaveraged 493° C. The average yields of pyrolysis products are, in mass%;

gas—10.9;

liquid—44.4;

solid—44.7 (including steal cord wire).

The liquid product density is 0.890; the sulfur content 0.95%.

The system for the sulfur regeneration testing included equipment forcarrying out three sub-stages of catalytic reaction: three reactors, twoheaters and three coolers and also the exhaust gases source. The exhaustgases containing sulfur dioxide were produced by a motorcar (“Renault”)operating on diesel fuel. The exhaust gases were passed through anintermediate box and further transported by a blower into the reactor,where they displaced the air from the box and from the reactor, whichwas preliminarily filled up to ⅔ of its volume with catalyst. Then thecar was refueled by 6 kg pyrolytic liquid (6.7 liter) and continued towork (without motion) and burned all the fuel in 134 min. In the inlettube the exhaust gas was mixed with H₂S flow from a balloon, therebyforming the reaction mixture. The rate of the H₂S flow was 1.1 liter perminute, which corresponds to the flow of H₂S extracted from pyrolysisand gasification gases while 6 kg of liquid are produced. The molarratio between H₂S and SO₂ was 3.7:1, as it is in real conditions in therecycling process for discarded tires shown in FIG. 1.

The reactor-converter for the Claus catalytic reaction was a horizontalcylindrical vessel of 7 liters volume with side covers that was equippedwith a horizontal rotating shaft and with mixing blades. It was alsoprovided with devices for the charging and discharging of the catalyst,as previously discussed and can be heated electrically by means of aspiral located around its outer surface. In the first reactor theactivated alumina catalyst was used in the form of balls of 4.8 mmdiameter. The reaction mixture after the reactor was fed to the coolerand was cooled down to 140° C. The formed sulfur was condensed and fedto the separator (the lower empty part of the cooler). There the vaporsand gases were separated from sulfur and were fed to the tube heaterthat was heated by an electric coil up to 220° C., and was fed to thesecond preliminary heated reactor, which was similar to those describedabove. The catalyst mixture used was activated alumina and titaniumdioxide. After passing the reactor, the reaction mixture was fed to thesecond sub-stage cooler and after separation of the formed sulfur it wasfed to the third sub-stage. The residual hydrogen sulfide was directlyoxidized by injected air over the Superclaus oxidizing catalyst(α-alumina supported iron and chromium oxides) at 220° C. Further thereaction mixture was cooled in the third sub-stage cooler down to 140°C. and was separated from the condensed sulfur. For the extraction ofany H²S residue the exhaust gas was additionally fed to an absorberfilled with activated carbon of type GS Sulfursorb Plus with theaddition of Activated Carbon impregnated with soda caustic.

The following experimental results were obtained:

Amount of Regenerated Sulfur:

in the first sub-stage—164.2 g

in the second stage—87.0 g

in the third stage—18.1 g

in the adsorption stage H₂S—0.7 g

The total sulfur recovery was 99.7%.

The H₂S concentration in the cleaned exhaust gas was 7 ppm, which isless than the Occupational Safety and Health Administration (OSHA, USA)acceptable ceiling limit in the workplace (20 ppm). It is also less thanthe limit set by the National Institute for Occupation Safety and Health(NIOSH, USA), which recommends 10 ppm in the work place.

As discussed above, the total after-purification from H₂S could beobtained here using an activated carbon scrubber of greater capacity,where the hydrogen sulfide concentration can be decreased down to 0.1ppm and less, i.e. less than the allowable concentration in atmosphericair.

All the above description of the process, system and examples has beengiven for the purpose of illustration and is not intended to limit theinvention in any way. Many modifications can be effected to the variousprocess steps, materials and equipment, and many different raw materialsmay be processed, all without exceeding the scope of the invention.

1. A process for the recovery of sulfur according to claim 5, comprisingthe steps of: a) carrying out the combustion of said liquid pyrolysisproducts, thereby to obtain sulfur dioxide; b) reacting said sulfurdioxide with hydrogen sulfide recovered from said gases generated in thepyrolysis process and from said generator gases; thereby to obtainelemental sulfur and, pure gaseous fuel essentially free fromsulfur-containing compounds, wherein the total sulfur recovery is atleast 99%.
 2. A process according to claim 5, wherein sulfur dioxide iscontained in exhaust gases formed in a diesel electro-generator.
 3. Aprocess according to claim 5, wherein the sulfur dioxide formed duringcombustion of pyrolysis liquid products, reacts with the recoveredhydrogen sulfide in three sub-stages over catalysts selected from thegroup consisting of: an activated alumina, a mixture of activatedalumina with titanium oxide (1:1) and, a catalyst comprising iron andchromium oxides supported by α-alumina or silica.
 4. A process accordingto claim 5, being an efficient electrical power production process,wherein: a) the fuels, which are employed, comprise gaseous and liquidfractions of pyrolysed tire shreds; b) the liquid fraction obtained froma pyrolysis step is used directly for power production; c) the gaseousfraction of the pyrolysis products, and the gas generated during thegasification of solid pyrolysis products are cleaned from hydrogensulfide, using the monoethanolamine process or other similar process,resulting in a hydrogen sulfide stream and in a clean gaseous stream;and d) the exhaust gases from the power production of step b) are mixedwith said hydrogen sulfide stream of step c), and reacted in a modifiedClaus process, such that essentially no sulfur-containing compounds arereleased into the atmosphere; wherein said final exhaust gases are freeof sulfur dioxide, and comprise less than 20 ppm hydrogen sulfide,preferably less than 10 ppm, and more preferably less than 1 ppm.
 5. Anenvironmentally friendly and energy-efficient process for the pyrolysisof sulfur-containing organic materials and for recovery of sulfur,wherein; a) the output of the pyrolysis, carried out in a pyrolyticreactor, comprises gaseous, liquid and solid sulfur-containing products;b) said liquid product is used as a fuel for electric power generation,producing after its combustion exhaust gases containing sulfur dioxide;c) the said solid, carbonized product is gasified, whereby obtaininggenerator gas which is used as a heat carrier for heating the rawmaterial in said pyrolytic reactor; d) said gaseous product in mixturewith said generator gas, partly cooled after separation from saidcondensed liquid product, after leaving said pyrolytic reactor,undergoes cleaning from hydrogen sulfide and provides a hydrogen sulfidestream, and a pure gaseous fuel for electric power generation, saidgaseous fuel producing after its combustion final exhaust gasesessentially free from sulfur or sulfur-containing compounds; and e) saidhydrogen sulfide stream reacts with said exhaust gases containing sulfurdioxide and provide regenerated elemental sulfur said environmentallyfriendly process producing electrical power in said steps b) and d),pure sulfur in said step e), and final exhaust gases essentially free ofsulfur or sulfur-containing compounds in said step d).
 6. A processaccording to claim 5, wherein said sulfur-containing raw organicmaterials for pyrolysis are selected from discarded tires, other sulfurvulcanized polymers, natural materials such as coals, oil shales,bitumen, and mixtures thereof.
 7. A process according to claim 6,wherein the liquid product of pyrolysis is of a quality suitable forburning either in engine electro-generators or in suitable furnaces forsubsequent power generation.
 8. A process according to claim 6, whereinsaid raw material comprises discarded tires, and wherein the solidproduct of the pyrolysis consists of solid carbonized component, andsteel component in the form of wire cuts from tires cord.
 9. A processaccording to claim 8, wherein the solid carbonized product directed togasification is first crushed and separated from the steel by sieving orby electromagnetic separation.
 10. A process according to claim 9,wherein the solid carbonized product is gasified in gas generators withraised or with horizontal flows or with pseudo-liquefied (boiling) bedusing only air or oxygen blowing, or blowing of said gases with steam,resulting in up to 950-1000° C. hot gaseous fuel containing sulfur inthe form of hydrogen sulfide.
 11. A process according to claim 10,wherein the hot generator gas is fed to a chamber to obtain a gaseousheat carrier by mixing with the final cool gas of the process so as toform-a gaseous heat carrier having a temperature of 650-700° C. fordirectly heating the pyrolytic reactor, or having a temperature of700-800° C. for indirectly heating the pyrolytic reactor.
 12. A processaccording to claim 5, wherein the heat of exhaust gases, formed in thecleaned gaseous mixture combustion and in the liquid pyrolysis productcombustion, are utilized as a heat carrier for the sulfur regenerationprocess.
 13. A process according to claim 5, wherein saidsulfur-containing organic materials comprise discarded tires, andwherein in step e) said hydrogen sulfide is in excess over said sulfurdioxide, in a molar ratio of up to 3.7:1.
 14. A process according toclaim 5, wherein residual amounts of hydrogen sulfide is removed fromthe processed exhaust gas in step d) using a sorbent consisting ofactivated carbon or its mixture with impregnated activated carbon,further comprising the regeneration of said sorbent, and addingregenerated hydrogen sulfide to said stream provided in step d).
 15. Aprocess according to claim 5, wherein the heat for sulfur regenerationprocess in all its sub-stages is provided by exhaust gases.